Deterioration in brain and heart functions following a single sub-lethal (0.8 LCt50) inhalation exposure of rats to sarin vapor: a putative mechanism of the long term toxicity.

The main injuries among victims of the terrorist act in the Tokyo subway resulted from sub-lethal inhalation and whole body exposure to sarin vapor. In order to study the long term effects of such exposure and to simulate these conditions, freely moving rats were exposed to sarin vapor (27.2±1.7 µg/l) for 10 min. About 50% of the rats showed no overt symptoms and the rest had mild to moderate clinical symptoms that subsided within 4h following exposure. A reduction of weight was noted during the first 3 days with full recovery on the 4th day. Rat's heart was challenged with epinephrine 1 and 6 months post exposure. A significant reduction in the threshold for epinephrine-induced arrhythmia (EPIA) was noted in rats exposed to sarin. A time dependent increase in the kD and Bmax values of muscarinic auto receptors (M2) was recorded in the rat's cortex and striatum. No changes were recorded in the rats' brain trans locator protein (TSPO) levels, concomitant with no observed changes in the animals' performance in A Morris water maze test. A significant increase in open field activity was noted 6 months following exposure to sarin vapor as well as a significant decrease in prostaglandin E2 (PGE2) production in the brain. It is speculated that down regulation of the M2 auto receptor function, caused hyper reactivity of the cholinergic system which leads to the changes described above. The continuous reduction in M2 auto-receptor system through an unknown mechanism may be the cause for long lasting decline in sarin-exposed casualties' health.

A novel action of glucocorticosteroid in inhibition of leukotriene C4 production by rat basophilic leukemia cells: suppression of the elevation of cytosolic free Ca2+ induced by antigen.

Rat basophilic leukemia (RBL-2H3) cells serve as a model to examine the role of elevated internal Ca2+ concentration ([Ca2+]i), following antigen (DNP10BSA)-induced stimulation of leukotriene C4 (LTC4) formation. A novel action of hydrocortisone (HC), to reduce increased [Ca2+]i and consequently inhibit LTC4 formation is assessed. Half-maximal time for elevation of [Ca2+]i induced by antigen was less than 1 min, and maximal elevation of [Ca2+]i (3-fold increase) was reached within 2-3 min. This high [Ca2+]i level waned gradually by 27% during 20 min of incubation. For induction of LTC4 formation, however, there was a refractory period of about 2 min, and half-maximal elevation was at 11 min. Following pretreatment with HC, the antigen-stimulated increase in [Ca2+]i was stunted by 41% at 2-3 min and by 73% at 20 min. LTC4 formation was almost abolished. There was a lag period of at least 2 h to observe any inhibition in both parameters, and the maximal inhibition was about 4 h. Cycloheximide, and receptor antagonist to glucocorticosteroid (RU486) completely prevented the inhibitory effects of HC on elevated [Ca2+]i and LTC4 formation. Estradiol and aldosterone (each at 2.10(-6) M) were virtually inactive, while another glucocorticosteroid, dexamethasone (2.10(-7) M) markedly suppressed antigen induction in both parameters. It is proposed that the inhibitory effect of HC on the formation of LTC4 could be attributed mainly to its ability to reduce elevated [Ca2+]i.

Acute and long-lasting cardiac changes following a single whole-body exposure to sarin vapor in rats.

Epinephrine-induced arrhythmias (EPIA) are known to be associated with local cardiac cholinergic activation. The present study examined the development of QT prolongation and the effect on EPIA of whole-body exposure of animals to a potent acetylcholine esterase inhibitor. Freely moving rats were exposed to sarin vapor (34.2 +/- 0.8 microg/liter) for 10 min. The electrocardiograms (ECG) of exposed and control animals were monitored every 2 weeks for 6 months. One and six months post exposure, rats were challenged with epinephrine under anesthesia, and the threshold for arrhythmias was determined. Approximately 35% of the intoxicated rats died within 24 h of sarin exposure. Additional occasional deaths were recorded for up to 6 months (final mortality rate of 48%). Surviving rats showed, agitation, aggression, and weight loss compared to non-exposed rats, and about 20% of them experienced sporadic convulsions. Sarin-challenged rats with severe symptoms demonstrated QT segment prolongation during the first 2-3 weeks after exposure. The EPIA that appeared at a significantly lower blood pressure in the treated group in the first month after intoxication lasted for up to 6 months. This decrease in EPIA threshold was blocked by atropine and methyl-atropine. Three months post exposure no significant changes were detected in either k(D) or B(max) values of (3)H-N-methyl scopolamine binding to heart homogenates, or in the affinity of carbamylcholine to cardiac muscarinic receptors. The increase in the vulnerability to develop arrhythmias long after accidental or terror-related organophosphate (OP) intoxication, especially under challenging conditions such as stress or intensive physical exercise, may explain the delayed mortality observed following OP exposure.

Diethylstilbestrol-elicited accumulation of cyclic AMP in incubated rat hypothalamus.

Diethylstilbestrol (DES) and 17beta-estradiol elicit significant increases in levels of endogenous and [14C]cyclic AMP in [14C]adeninelabeled hypothalami from immature female rats, but only after incubation of the hypothalami with these estrogenic agents for 40-50 min. Estriol has no effect. The 2-fold accumulation of cyclic AMP elicited by low concentrations (20 muM) of DES appears dependent on catecholamine-related mechanisms, since it is prevented by either alpha- or beta-adrenergic antagonists. Higher concentrations (100 muM) of DES elicit a 3-fold accumulation of [14C]cyclic AMP which is only partially blocked by adrenergic antagonists, haloperidol, or the adenosine antagonist, theophylline. These phenomena appear to be specific for the hypothalamus since incubation of cerebral cortical slabs with estrogens resulted in no significant increases in the levels of cyclic AMP. The slow time course in whole hypothalami and the complete lack of effects of low concentrations of estrogenic agents in chopped hypothalami suggest an indirect mechanism of action. Interaction of estrogens with receptors in cell bodies may result, after a latent period of 40-50 min, in enhanced release of catecholamines from distal synaptic terminals and in stimulation of catecholamine-sensitive adenylate cyclases at post-synaptic sites.

Differential regulation of mu-opiate receptors in heroin- and morphine-dependent rats.

Rats made dependent on heroin and morphine exhibit both qualitative and quantitative differences in the characteristics of radioligand binding to mu-opioid receptors in the central nervous system. In brain membranes prepared from control animals, [3H]dihydromorphine (DHM) binding was best described by a two-site model, while in morphine-dependent rats, [3H]DHM binding was best described by a single-site model. In contrast, [3H]DHM binding to membranes from heroin-dependent animals was best described by a two-site model, with an increased density of the high-affinity, and no change in the low-affinity population compared to controls. Furthermore, both the number of binding sites for [3H]DAGO (a ligand that selectively labels a population of high-affinity mu-opiate receptors) and the sensitivity of [3H]DHM to sodium ions was increased in heroin; but not in morphine-dependent rats. These studies demonstrate that opiate receptors are differentially regulated in heroin- and morphine-dependent animals. Such neurochemical changes in mu-opiate receptors may underlie differences in the behavioral and pharmacological profiles of heroin and morphine reported in man.

Interactions between nitrogen oxide-containing compounds and peripheral benzodiazepine receptors.

Nitrogen oxide-containing compounds displaced the peripheral benzodiazepine ligand [3H]Ro5-4864 from guinea pig membrane preparations. Sodium nitroprusside (SNP) was the most potent (IC50 = 5.61 +/- 1.72 x 10(-5) M). Moreover, its ability to bind to these receptors showed marked tissue variability (heart greater than kidney much greater than cerebral cortex). When tested on rat atrium, SNP by itself had no effect on basal inotropy or the increase in inotropy induced by (-)-S-BAY K 8644. In contrast, Ro5-4864 potentiated the marked increase in inotropy induced by (-)-S-Bay K 8644, and SNP completely abolished the potentiation of inotropy observed with Ro5-4864. Since peripheral benzodiazepine receptors are associated with calcium mobilization in the heart, these findings may indicate that some of the clinical effects of nitric oxide-generating drugs could be mediated by these receptors.

Endogenous inhibitors of 4'-[3H]chlorodiazepam (Ro 5-4864) binding to 'peripheral' sites for benzodiazepines.

'Peripheral' binding sites for benzodiazepines are under neural or homonal control in the pineal gland, olfactory bulb, and kidney. These observations prompted a search for an endogenous substance which could modulate these sites under physiological conditions. Acidified methanol extracts from several tissues (e.g. stomach, kidney, lung) were found to inhibit the binding of [3H]Ro 5-4864 to 'peripheral' binding sites, but did not significantly affect the binding of [3H]diazepam to 'brain' benzodiazepine receptors. Fractionation of a crude extract prepared from antral stomach by either ultrafiltration or gel filtration chromatography yielded high (Mr greater than 10 000) and low (Mr less than 1000) Mr fractions which competitively inhibited [3H]Ro 5-4864 binding to 'peripheral' sites. These observations suggest the presence of endogenous substances in several rat tissues which may represent physiologically important ligands for 'peripheral' binding sites for benzodiazepines.

Age-related changes in the cholinergic components within the central nervous system. II. Working memory impairment and its relation to hippocampal muscarinic receptors.

Cognitive performance in aging Wistar rats was monitored using the radial arm maze and the latter was correlated with the density of muscarinic receptors in the CNS, using quantitative in vitro receptor autoradiography. Significant working memory deficits were observed in 12, 17 and 24-month-old rats as compared to 3-month-old animals. In addition, the number of the muscarinic receptors declined significantly with age (from 27 to 42% depending on the brain region sampled) utilising [3H]QNB and [3H]PZ receptor binding assays. The above trend became evident already at the age of 12 months. The present findings support the association of central cholinergic activity with memory processes.

New analgesic drugs derived from phencyclidine.

Several esters of 1-(1-phenylcyclohexyl)-4-piperidinol (3), 1-(1-phenylcyclohexyl)-4-phenyl-4-piperidinol (10) and its propionate (11), and 1-(1-phenylcyclohexyl)-4-phenylpiperidine (13) were prepared and characterized. The new compounds, which are derived from phencyclidine, exerted analgesic activity in mice. The most potent is 10, which is twice as active as morphine. The antinociceptive activity of 10, 11, and 13 could be well correlated with their potency in the mouse vas deferens bioassay, and both were completely reversed by naloxone.

Probes for narcotic receptor mediated phenomena. 9. Synthesis of (+/-)-(3 alpha,6a alpha,11a beta)-1,3,4,5,6,11a-hexahydro-2-methyl-2H-3,6a- methanobenzofuro[2,3-c]azocin-10-ol, an oxide-bridged 5-(m-hydroxyphenyl)morphan.

The synthesis of racemic (3 alpha,6a alpha,11a beta)-1,3,4,5,6,11a- hexahydro-2-methyl-2H-3,6a-methanobenzofuro[2,3-c]azocin -10-ol (2d) is described. The route used acid-catalyzed ring closure of enamine 5 to yield the unsaturated phenylmorphan 6. Conversion of 6 to oxide-bridged 2d was accomplished in a multistep fashion that utilized the introduction of a bromine atom, followed by O-demethylation of the phenolic methyl ethers and base-catalyzed intramolecular phenoxide displacement of the bromine. Compound (+/-)-2d represents an oxide-bridged derivative of the potent 5-(m-hydroxyphenyl)morphan class of opioid analgesics 1. Unlike the 5-(m-hydroxyphenyl)morphans that have a freely rotating phenyl group, 2d has the phenyl ring conformationally restricted at an angle of 49 degrees relative to atoms 1, 3, 11a, and 12 of 2d. The low binding of (+/-)-2d to rat brain homogenate receptor preparations [IC50 = 1000 nM] may indicate that the phenyl angle of 49 degrees is not suitable for binding to opioid receptors.

Diffusion of oxygen in human corneas in vivo.

No oxygen was detected on the corneal surface of human subjects breathing air or almost pure oxygen. These results suggest that the epithelium obtains all its oxygen fro the air or the palpebral conjunctiva and that the endothelium is supplied with oxygen solely by the aqueous humor.

In vivo aqueous humor oxygen tension--as estimated from measurements on bare stroma.

Aqueous humor oxygen tension of the in vivo rabbit eye was estimated by a relatively atraumatic procedure. The anterior corneal surface of the eye was first scraped free of its epithelial layer. A polarographic oxygen electrode was then used to measure the oxygen tension at the bare stromal surface. Aqueous humor oxygen tension can be estimated from this measured steady-state stromal surface oxygen tension by correcting the measured oxygen tension for the tension drop across the stroma and endothelium. When animals breathed room air (155 mm Hg oxygen tension), the oxygen tension of the aqueous humor was 13 mm Hg; this rose to 150 mm Hg when the inspired oxygen tension was 713 mm Hg.

Oxygen permeability of collagen shields.

The oxygen permeability (Dk) of ten 24-hr collagen shields was measured directly by polarographic methodology at approximately 2 hr of hydration. Edge and boundary effects were included in the calculations. Dk was found to be approximately 26 x 10(-11) cm ml O2/sec ml mmHg at 35 degrees C. Mean water content of the shields was 65.7% (SD = 1.0%) as measured by a hand refractometer. Therefore, the projected oxygen transmissibility of collagen shields is expected to be compatible with normal corneal metabolism.

Oxygen permeability of rabbit and human corneal stroma.

Oxygen permeability (Dk) of 15 rabbit and 19 human cornea stromal samples was measured by conventional polarographic means at 36 C. Hydration and thickness were also measured. Rabbit stromal permeability was found to be about 26 X 10(-11) ml O2 cm2/sec ml mmHg at normal in vivo hydration; in vivo human cornea stromal permeability is probably less than 29 X 10(-11) ml O2 cm2/sec ml mmHg.

Monoaminergic involvement in the pharmacological actions of buspirone.

Buspirone, MJ-13805 and MJ-13653 did not produce a '5-hydroxytryptamine (5-HT) syndrome' in rats at doses up to 20 mg kg-1. These drugs were very weak 5-HT uptake blockers (IC50 much greater than 10 microM) compared to drugs such as chlorimipramine. These drugs did not inhibit either monoamine oxidase (MAO)-A or MAO-B. The Ki values for these agents as inhibitors of [3H]-5-HT and [3H]-ketanserin binding to rat frontal cortex or hippocampal membranes were in the microM range, well above the brain concentrations achieved after an oral dose of 25 mg kg-1. Parenterally administered buspirone blocked apomorphine-induced stereotypy, inhibited the 5-HT syndrome elicited by 5-methoxy-N,N-dimethyltryptamine, and delayed the onset of p-chloroamphetamine induced behaviours.

Bay K 8644-induced changes in the ECG pattern of the rat and their inhibition by antianginal drugs.

1. The effects of intracarotid administration of Bay K 8644 on the ECG pattern along with their reversal by antianginal drugs were investigated in anaesthetized rats. 2. Intracarotid injections of Bay K 8644 (0.5-50.0 micrograms kg-1) produced a dose-related transient increase in systemic blood pressure. 3. The pressor response was accompanied by ST segment elevation (0.5-10.0 micrograms kg-1), ST segment depression concomitant with the occurrence of arrhythmias (20.0 micrograms kg-1), or A-V block (50.0 micrograms kg-1). 4. ST segment elevation reached its maximal value within 15 s and could be observed for 30-240 s. 5. The increase in blood pressure was immediate (within 5 s) and short lasting (30-120 s). After the initial increase it returned to control levels (0.5-20.0 micrograms kg-1) or dropped below (50.0 micrograms kg-1). 6. The ST segment elevation caused by 5.0 micrograms kg-1 Bay K 8644 (submaximal dose) was blocked by antianginal drugs (e.g. nitroglycerin, nifedipine and diltiazem) and by the peripheral benzodiazepine receptor antagonist PK 11195. However, the pressor response was not blocked by any of the drugs used. 7. ST segment elevation (or depression) induced by intracarotid administration of Bay K 8644 provides a useful tool for the evaluation of potential antianginal drugs.

Aprophit: an irreversible antagonist for muscarinic receptors.

The development of selective irreversible ligands has proven to be an invaluable technique for the isolation, purification and characterization of many receptor proteins. An isothiocyanato-derivative of the muscarinic antagonist aprophen was synthesized and evaluated as a potential irreversible ligand for muscarinic receptors. This compound (aprophit) displaced [3H]N-methylscopolamine binding from rat cerebral cortex with a Ki of 3.1 x 10(-7) M. The inhibition was concentration-dependent and could not be reversed by extensive washing. Aprophit inhibited the acetylcholine-stimulated release of catecholamines from isolated, perfused guinea pig adrenal glands in a concentration-dependent manner. This inhibition was not reversed by perfusing the tissue with Locke's solution and was not due to a non-selective acylation by the isothiocyanate function. The data suggest that aprophit is selectively acylating muscarinic receptor proteins and thus may be useful in their further characterization.

Oxygen transmissibility, thickness, and water content of three types of collagen shields.

Oxygen transmissibility, thickness, and water content were measured for three types of collagen shields: six of each type designed to dissolve in 12, 24, and 72 hours. Oxygen transmissibility was measured by a polarographic method at 35 degrees C and was found to be 17.9, 17.3, and 23.8 x 10(-9) cm mL O2/s mL mm Hg, respectively. Thicknesses were measured with an electronic gauge, and the central thicknesses of the 12-hour shields were found to be significantly greater (mean thickness, 0.19 mm) than the central thicknesses of the other two types (0.15 mm each). Water content, as measured by a hand refractometer, was found to be about 63% for all three types of shields, and no statistically significant differences were found. These measurements indicate that collagen shields behave like 63% water-content hydrogel contact lenses (oxygen permeability estimated at 27 x 10(-11) cm2 mL O2/s mL mm Hg) with regard to oxygen transmission.

The effectiveness of daily wear contact lenses for the correction of infantile aphakia.

OBJECTIVE: To evaluate the effectiveness and safety of daily wear contact lenses in the treatment of infantile aphakia. DESIGN: A study of prognosis using a cohort followed up for a mean of 58 months. SETTING: All operations, contact lens care, and follow-up were conducted at a university referral center. PATIENTS: Of 111 children undergoing surgery for cataract between 1980 and 1990, 51 (68 eyes) met the criteria of age younger than 2 years at the time of surgery and of cataract of nontraumatic origin. Patients were evaluated for visual acuity, complications, number of contact lenses worn per year, and changes in contact lens refractive power per month. A subgroup of 28 eyes of patients undergoing surgery before age 7 months and followed up for at least 24 months was studied. INTERVENTION: Following cataract surgery, all patients were fitted with daily wear contact lenses. MAIN OUTCOME MEASURE: Final visual acuity and complications were studied. The distribution of mean contact lens power for each month of age was determined. RESULTS: During the follow-up period, no serious complications were encountered. The visual acuity outcome was better following bilateral cataract surgery than unilateral surgery (P < .001 using chi 2 analysis) and was comparable with that achieved with extended wear contact lenses. CONCLUSION: Daily wear contact lenses were found to be safe and effective in the treatment of infantile surgical aphakia. The daily care was easily learned by the parents.

Humoral-endorphin blood levels in autistic, schizophrenic and healthy subjects.

Basal morning humoral (H)-endorphin blood levels were assessed in ten autistic patients, 12 chronic schizophrenic patients and 11 healthy control subjects. Four autistic patients and four schizophrenic patients were drug free for at least 6 months while all other psychiatric patients were under treatment with antidopaminergic agents. Significantly reduced opioid levels were observed in the autistic group (827 +/- 103 vs 1121 +/- 75 pg-eq/ml, P less than 0.025), although the difference was actually only 26% of the control mean. A similar tendency toward low H-endorphin levels was also observed in the schizophrenic patients; however this difference was not significant (919 +/- 129 vs 1121 +/- 75 pg-eq/ml; NS). No significant difference was obtained between subjects suffering from the two psychiatric disorders (827 +/- 103 vs 919 +/- 129 pg-eq/ml; NS). Various interpretations of the decreased secretion of H-endorphin are discussed.